Flame retardants are used with a wide variety of polymers to improve their flammability performance. In the past, for example, halogenated (e.g., brominated) flame retardants were employed. Recent attempts have been made, however, to find substitute flame retardants that are generally free of halogens. For example, phosphinic acid salts have been employed as halogen-free flame retardants. Unfortunately, such phosphinic acid salts tend to lead to a deterioration in mechanical strength and elongation when used in the quantities needed to achieve optimum flammability performance. As such, a need remains for a flame retardant that is generally free of halogens and that is also able to achieve good mechanical properties.